Histological Validation of measurement of diffuse interstitial myocardial fibrosis by myocardial extravascular volume fraction from Modified Look-Locker imaging (MOLLI) T1 mapping at 3 T

Abstract

Background: Gadolinium (Gd) Extracellular volume fraction (ECV) by Cardiovascular Magnetic Resonance (CMR) has been proposed as a non-invasive method for assessment of diffuse myocardial fibrosis. Yet only few studies used 3 T CMR to measure ECV, and the accuracy of ECV measurements at 3 T has not been established. Therefore the aims of the present study were to validate measurement of ECV by MOLLI T1 mapping by 3 T CMR against fibrosis measured by histopathology. We also evaluated the recently proposed hypothesis that native-T1 mapping without contrast injection would be sufficient to detect fibrosis. Methods: 31 patients (age∈=∈58∈±∈17 years, 77 % men) with either severe aortic stenosis (n∈=∈12) severe aortic regurgitation (n∈=∈9) or severe mitral regurgitation (n∈=∈10), all free of coronary artery disease, underwent 3 T-CMR with late gadolinium enhancement (LGE) and pre- and post-contrast MOLLI T1 mapping and ECV computation, prior to valve surgery. LV biopsies were performed at the time of surgery, a median 13 [1-30] days later, and stained with picrosirius red. Pre-, and post-contrast T1 values, ECV, and amount of LGE were compared against magnitude of fibrosis by histopathology by Pearson correlation coefficients. Results: The average amount of interstitial fibrosis by picrosirius red staining in biopsy samples was 6.1∈±∈4.3 %. ECV computed from pre-post contrast MOLLI T1 time changes was 28.9∈±∈5.5 %, and correlated (r∈=∈0.78, p∈